Light control device for high frequency lighted fluorescent lamp

Abstract

A light control device for a high frequency lighted fluorescent lamp includes a high frequency variable voltage power source. A first impedance element (a capacitor and inductor in series) is provided between the terminals of the lamp on the side opposite to the power source. A second impedance element (an inductor) is connected between the power source and the terminals of the lamp, and a third impedance element (a capacitor) is connected across the lamp on the power source side. A constant power source circuit supplies, upon starting of the lamp, constant power to the first impedance element to thereby apply substantially constant cathode pre-heating current and starting voltage and applies, during the lighting of the lamp, substantially constant cathode heating current. The control circuit is capable of pre-set light control. The light control device suppresses beat interference and fluorescent lamp noises due to the electric field radiated from the lamp. Rapid and instant starting is enabled. The solid state ballast is suitable for fluorescent lamp appliances for domestic use and permits use as an emergency lamp.

What is claimed is: 
     
       1. A light control device for a high frequency lighted fluorescent lamp, comprising: a high frequency variable voltage power source, a first impedance element provided on both terminals of a fluorescent lamp on the side opposite to said power source, a constant power source circuit which supplies, upon starting of the lamp, a constant power to said first impedance element to thereby apply substantially constant cathode pre-heating current and starting voltage and applies, during lighting of the lamp, substantially constant cathode heating current by the lamp voltage, and capable of pre-set light control. 
     
     
       2. The light control device for high frequency lighted fluorescent lamp as defined in claim 1, wherein the constant power source circuit comprises a high frequency variable voltage power source, a second impedance element connected between said power source and the terminals of the fluorescent lamp on the power source side, the fluorescent lamp and the first impedance element. 
     
     
       3. The light control device for high frequency lighted fluorescent lamp as defined in claim 1, wherein the constant power source circuit comprises a high frequency variable voltage power source, a second impedance connected between said power source and the terminals of the fluorescent lamp on the power source side, a third impedance element connected in series with the power source side terminals of the fluorescent lamp, the fluorescent lamp and the first impedance element. 
     
     
       4. The light control device for high frequency lighted fluorescent lamp as defined in claim 3, wherein the first impedance element is a serial circuit composed of a first coil and a first capacitor, the second impedance element is a second coil provided in a magnetic path in common to said first coil and the third impedance is a second capacitor. 
     
     
       5. The light control device for high frequency lighted fluorescent lamp as defined in claim 2, wherein the first impedance element is a circuit consisting of a serial circuit composed of a first coil and a first capacitor and a second capacitor further connected in parallel therewith. 
     
     
       6. The light control device for high frequency lighted fluorescent lamp as defined in claim 3, comprising a pair of fluorescent lamps, which operate in a sequential manner and wherein the first impedance element comprises two sets of serial circuits, each provided between said terminals of a respective lamp on the side opposite to said power source, and each composed of a first coil and a first capacitor, and the second impedance element is a second coil provided in a magnetic path in common to said first coils and the third impedance element is composed of two sets of second capacitors, each connected across a respective one of said series circuits. 
     
     
       7. The light control device for high frequency lighted fluorescent lamp as defined in claim 2, comprising a pair of fluorescent lamps which operate in a sequential manner and, wherein the first impedance element is two sets of circuits, each provided between said terminals of a respective lamp on the side opposite to said power source, and each consisting of a serial circuit composed of a first coil and a first capacitor and a second capacitor further connected in parallel therewith, and the second impedance element is a second coil provided in a magnetic path in common to the first coils. 
     
     
       8. The light control device for high frequency lighted fluorescent lamp as defined in claim 1, wherein the high frequency variable voltage power source comprises a variable output AC-DC converter and a fixed frequency - sine wave - input proportional amplitude inverter. 
     
     
       9. The light control device for high frequency lighted fluorescent lamp as defined in claim 1, wherein the high frequency variable voltage power source comprises a circuit for the direct rectification and filtration of a commercial power source and a fixed frequency - sine wave - variable output inverter. 
     
     
       10. A variable output AC-DC converter for use with the light control device for high frequency lighted fluorescent lamp as defined in claim 8, which is adapted to conduct only in the range of the phase angle between π/2-π of the power source voltage in which the angle of conduction is set small enough as compared with 2π and the conduction phase is rendered variable to thereby substantially equalize the terminal voltage of a smoothing capacitor to the instantaneous value of the power source voltage in the conduction phase. 
     
     
       11. A collective light control device for high frequency lighted fluorescent lamp as defined in claim 8, capable of load wiring in a 2-line system of non-polarity connection wherein the outputs from a control circuit adapted to conduct only in the range of the phase angle between π/2-π of the power source voltage and the conduction phase of which is rendered variable, are supplied respectively to individual fixed frequency - sine wave - DC input proportional amplitude inverters each having a built-in rectification and filtration circuit using a diode bridge. 
     
     
       12. The light control device for high frequency lighted fluorescent lamp as defined in claim 1, wherein the high frequency variable voltage power source comprises variable output (output-switchable) DC sources controlled by a sensor and a fixed frequency - sine wave - input proportional amplitude inverter, and having a function of an emergency lamp. 
     
     
       13. The light control device for high frequency lighted fluorescent lamp as defined in claim 12, which is adapted to perform a selective power feeding on the high voltage side by supplying a power to a fixed frequency - sine wave - input proportional amplitude inverter from two sets of DC power sources of different voltages respectively by way of a blocking diode.